It is known that in an internal combustion engine, a combustion charge of fuel and air is drawn into the combustion chamber (cylinder) through one or more intake valves. After combustion, the resulting burned gases are exhausted from the cylinder through one or more exhaust valves. The measure of how efficiently the engine can move the air/fuel charge into and out of the cylinder is referred to as the volumetric efficiency (VE). The VE is usually expressed as a percentage, and describes the volume of air charge that actually enters the cylinder during induction as compared to the cylinder volume. For control of the engine air/fuel ratio, an electronic engine controller or the like needs to have an estimate of the VE so that it can generate an accurate estimation of the mass airflow entering the combustion chamber. Conventional approaches estimate the VE as a function of engine speed and an engine pressure ratio (i.e., exhaust pressure/intake pressure). The engine pressure ratio is used as a load dependency in the VE calculation since this is widely thought to effectively combine the boundary conditions of relevance on volumetric efficiency while including altitude dependency.
However, engine pressure ratio does not change monotonically with engine load for a turbo-charged engine, and is therefore not a suitable model form for all air induction configurations.
There is therefore a need for a system and method for a volumetric efficiency model that minimizes or eliminates one or more of the problems set forth above.